The invention relates to an arrangement for adjusting the value of an electrical component by means of a rotatable driven shaft having a first angle of rotation to produce a change from a first to a second value by means of a control member having a second angle of rotation, the arrangement comprising a first pulley mounted on the shaft of the component, a second pulley coupled to the control member and a cord which extends round the first and second pulleys to transmit rotary motion from the second pulley to the first pulley, the ratio of the core or groove diameters of the pulleys being determined by the desired ratio of the first and second angles of rotation.
In television studio and outside broadcast equipment such as video tape recorders, special effects generators and remote controllers it is frequently desired to utilise the full rotation of a rotary potentiometer, which is typically 300.degree., while using a control lever which has a smaller sweep angle, for example 60.degree.. Arrangements which have previously been used to achieve this adjustment have involved the use of gear trains, the use of pulley and cord arrangements or the use of friction drums. All these arrangements have disadvantages. Gear trains suffer from backlash and friction drums and pulley and cord arrangements suffer from slip between the components. In addition all these arrangements exert a side thrust on the spindle of the potentiometer causing roughness in operation of the potentiometer and a reduced life for the resistance track and wiper.